I've been iterating from using Gdocs towards simple dated text files. Last year it was by quarter, this year it's by month. I did have trouble with maintaining sync but finally bit the bullet this year and created a DigitalOcean instance dedicated to SyncThing hosting. SyncThing was working great previously just across phone and two local computers, but I had to remember to keep the remote machines active to have everything sync. So having one that I don't physically control is actually helpful.
The most important thing for me is to put dates, and sometimes times, on things. The second most important thing is, when I have a brainstorm, filter it into a coherent[0] set of ideas right then and there. My previous "idea generation" strategy held on too long to ideas that don't cohere. As a result I had many ideas that didn't go anywhere and weren't memorable. Making a coherence is much more powerful, since it creates a web of ideas that catch other ideas. My "hit rate" has improved a ton since I changed strategy.
I second the approach of using text files and syncthing.
Using a markdown editor on my phone and computers means I've always got access to view, edit and create new ones, even offline, that all sync up when I'm back online.
It works great and I'm not giving my data to anyone else.
The most important thing for me is to put dates, and sometimes times, on things. The second most important thing is, when I have a brainstorm, filter it into a coherent[0] set of ideas right then and there. My previous "idea generation" strategy held on too long to ideas that don't cohere. As a result I had many ideas that didn't go anywhere and weren't memorable. Making a coherence is much more powerful, since it creates a web of ideas that catch other ideas. My "hit rate" has improved a ton since I changed strategy.
[0] http://ludamix.com/dive/coherency/